Lithium medication during pregnancy is uncommon and the problems of a neonate who has been exposed to lithium represents a rare situation in neonatology. The clinical presentation and management of a newborn whose mother received lithium during pregnancy is presented. The newborn manifested a four day course of lethargy with unexplained high lithium levels in the adult toxic range. The infant improved clinically under intravenous hydration therapy, nevertheless lithium serum levels increased again and we did not know for certain if our clinical instinct or the actual figures were correct. Finally we noticed that our confusion had resulted from test tubes containing lithium heparine.